Synthesis, Structural Characterization, Theoretical Calculations and In Vitro Biological Activities of Organotin(IV) Complexes with [O,O] Donor Ligand

Abstract

The present study deals with the synthesis of ligand 4-oxo-4-(thiazol-2-ylamino)butanoic acid and afterward its organotin(IV) carboxylates [Bu3SnL] (1), [Ph3SnL] (2), [Me2SnL2] (3), [Bu2SnL2] (4) and [Ph2SnL2] (5). These complexes were characterized by useful techniques like elemental analysis, FT-IR, NMR (1H, 13C) and single crystal analysis. The ligand coordinates to tin atom via the carboxylate group. Complex 1 has also been studied by single crystal XRD analysis. It showed that tin has distorted tetrahedral geometry due to bulky butyl groups that hinder the carbonyl oxygen of the ligand interaction with the adjacent tin atom for further coordination. The HOMO–LUMO study of ligand “HL” and its tin complexes 3 and 5 indicated that tin complexes are thermodynamically more stable than the ligand. The synthesized complexes were screened for their biological activities like antibacterial, antifungal, antileishminial, cytotoxicity and protein kinase inhibition studies in vitro. Complexes 1 and 2 exhibited maximum antileishmanial activity that was even higher than that of standard Amphotericin B, with significant cytotoxicity and could be potential candidates for the treatment of leishmaniasis. The UV–visible spectroscopic studies revealed that ligand and its complexes bind with DNA via intercalative mode of interaction leading to hypochromism and minor bathochromic or hypsochromic shifts.